The ever pressing demand for increased functionality from integrated circuit chips requires an increase in the number of circuit components on each chip. To accommodate this need, circuit designers are continually searching for ways of reducing the number of components--usually transistors--required to perform a particular circuit function. One such circuit function is that of oscillators.
Applications for oscillators are widespread. Typically, the frequency of an oscillator is controlled by either a control current or a control voltage. The level of the control current or control voltage determines how quickly a capacitor is charged and discharged, thus providing the frequency of the oscillator.
Circuitry for controlling the charging and discharging of the capacitor comprises a large portion of the chip area taken up by the oscillator.